ENGI3703- Surveying and Geomatics Fall 2007

Memorial University of Newfoundland 1

Lab 2: Differential Leveling

Objective: To introduce the method of differential leveling and to learn basic techniques

of leveling, and to practice standard note taking protocol for fieldwork.

Preparation: Read chapters 4 and 5 in the Elementary Surveying, 11th ed. Textbook.

Instruments to be used: Check out the following equipment:

1. Automatic Level

2. Tripod 3. Leveling Rod

4. Simple calculator (your own)

Overview: Differential leveling is the most common method for measuring elevations of

monuments or objects (Figure 2.1). In this most commonly employed method,

a telescope with suitable magnification is used to read graduated rods held on

fixed points.

Figure 2.1 Differential leveling (Figure 5.4 in the textbook)

ENGI3703- Surveying and Geomatics Fall 2007

Memorial University of Newfoundland 2

Figure 2.2 Differential leveling notes for Figure 2.1 (Figure 5.5 in the textbook)

Procedure:

1. Students are divided into groups. One set of measured data to be recorded for each

group in one of the field books during the leveling procedure. However, each person

in the group must make a sketch in his/hers field book during the leveling procedure

(this will be checked by the TA). The measured data can be copied by each party in

his/hers own field book after fieldwork.

2. Locate the beginning benchmark (elev. = 59.854 m, latitude = 47°34’18”N, longitude

= 52°44’12”W) located close to the wall of the Education building, Memorial

university, at east side of intersection of westerland Road and Prince Phillip Drive,

tablet in north concrete foundation, 65 cm from northwest corner, 10 cm above ground

level. This will be your starting station and first backsight (BS). (See Figure 2.4).

ENGI3703- Surveying and Geomatics Fall 2007

Memorial University of Newfoundland 3

3. The instructor will assign an area for each group and each group will choose two

points in their own parcel. Mark these points by a wooden peg and conduct a level

loop to determine the elevation of these points and your starting point (BM).

4. Once the starting station is found and two points are identified, locate another suitable

turning point towards your assigned area to serve as a foresight (FS) station.

5. Set up your Level within sight of both stations, making sure you have even sight

distances. This is critical to assure even balance of the BS and FS. Be sure to securely

implant the tripod into the ground to minimize errors due to settlement.

6. Set the level rod on the BS station; to ensure that it is level, hold it lightly between the

tips of your fingers until it rocks very gently indicating it is perpendicular with the

gravitational surface (a rod level may also be used, if available). Your lab instructor

will show you how to do this if necessary.

7. Adjust the crosshairs so that they are clear and distinct when you look through the

eyepiece. See Figure 2.3 for a typical instrument layout. Direct the instrument towards

the level rod and adjust the focus knob until the rod is crisp and clear. You will have

to adjust the parallax for different instrument operators.

8. Take readings at the top, middle, and bottom line to the nearest millimeter and average

the top and bottom lines; these should be within a millimeter of your middle

observation. If not, there is a blunder in your reading and you must observe the station

again. Record the middle reading to your field book.

9. Repeat steps 7 and 8 for the foresight station. When you check your FS distance in

comparison to the BS, you should be within ±10 meters of having equal distance legs.

If not, you must move your foresight accordingly to create equal sight legs.

10. If within sight distance tolerance, LEAVE THE LEVEL ROD IN PLACE at the FS

station, pick up the level and repeat steps 5-9 sufficient times to reach to the two

points in your parcel.

11. Once you get to the two points in your parcel, repeat steps 5-9 in a loop to determine

the elevation of the starting point (BM).

ENGI3703- Surveying and Geomatics Fall 2007

Memorial University of Newfoundland 4

12. Perform a closure analysis on your loop. The loop misclosure should be less than

0.0062(m) x √n; where n is the number of instrument setups. Compare actual

misclosure with allowable and share with the TA prior to ending the lab. If your loop

misclosure exceeds the allowable value, you must repeat the measurements.

13. Adjust the error through the points as instructed in Figure 2.2 of this manual.

14. Pick up your equipment, clean and return it to the equipment room. Make sure your

notes are COMPLETE.

Figure 2.3 Parts of an automatic level (Figure 4.9 in the textbook)

ENGI3703- Surveying and Geomatics Fall 2007

Memorial University of Newfoundland 5

Figure 2.4 Location of the benchmark and individual parcels

G-2

G-1

G-3

G-4

G-5

G-6

BM